(1) Field of the Invention
The present invention relates to an etching apparatus, and more particularly to a radio frequency electron cyclotron resonance (RF.multidot.ECR) plasma etching apparatus for use in etching a surface of a wafer or a substrate with the plasma produced by utilization electron cyclotron resonance phenomena.
(2) Description of the Related Art
There are two examples of conventional microwave plasma etching apparatuses to which the present invention relates.
One such etching apparatus shown in FIG. 1 is disclosed in Japanese Patent Application Kokai Publication No. Sho 56-155535. In this apparatus, an ething object 101 is set where the electron cyclotron resonance discharge caused by microwaves 102 takes place for etching. In FIG. 1, a plasma-producing chamber is designated by numeral 103, a microwave inlet window by numeral 104, a waveguide by numeral 105, a gas inlet port by numeral 107, an electron cyclotron resonance point by numeral 109, and a substrate holder by numeral 110.
The other example shown in FIG. 2 is disclosed in Japanese Patent Application Kokai Publication No. Sho 60-134423. In this apparatus, a reaction gas is introduced into a plasma-producing chamber 201, and a reactive gas plasma is produced by the reaction of both the microwaves and the magnetic field in the plasma-producing chamber 201. By utilizing the divergent magnetic field generated by a magnetic coil, the produced reactive gas plasma is introduced into a reaction chamber 202 where the substrate 203 to be etched is placed. In FIG. 2, a solenoid coil for generating the divergent magnetic field is designated by numeral 204, a microwave inlet window by numeral 205, a waveguide by numeral 206, a microwave source by numeral 207, a gas inlet duct by numeral 208, an electron cyclotron resonance point by numeral 209, a substrate holder by numeral 210, a plasma introduction window by numeral 211, and an exhaust duct by numeral 212.
However, in each of the above conventional apparatuses, a microwave emission of 2.45 GHz is used thereby requiring a waveguide and, in order to cause the resonance to occur, a magnetic field intensity in the order of 900 Gausses is required. One of the problems therefore is that the apparatus inevitably becomes large and complex. Also, there are difficulties in uniformly introducing microwaves and in uniformly producing plasma. Furthermore, since the magnetic line of force is applied perpendicular to the substrate, there are problems involving occurrence of potential distribution or difficulties in the uniform application of radio frequency bias to the substrate.